Earthing solar panels

[Chris_S]

What is the SANS rules on this? 

Can panels be connected to house earth or must they have a dedicated earth spike. 

My home earth is connected to utility earth and a ground spike. Can I just use this existing ground spike? 

[BritishRacingGreen]

42 minutes ago, Chris_S said:

What is the SANS rules on this? 

Can panels be connected to house earth or must they have a dedicated earth spike. 

My home earth is connected to utility earth and a ground spike. Can I just use this existing ground spike? 

I think it is a requirement. In any case the seperate earth spike and routing is safer for you and your building. Remember the lightning attack surface on pv frames is huge, and you will want the high current surges not to enter your building inner, rather arrest it via a seperate route. 

[Chris_S]

10 minutes ago, BritishRacingGreen said:

I think it is a requirement. In any case the seperate earth spike and routing is safer for you and your building. Remember the lightning attack surface on pv frames is huge, and you will want the high current surges not to enter your building inner, rather arrest it via a seperate route. 

Can I use 1 spike for all strings? And do you know if I must use bare copper cable or will insulated 6mm2 house wire be OK? 

[BritishRacingGreen]

23 minutes ago, Chris_S said:

Can I use 1 spike for all strings? And do you know if I must use bare copper cable or will insulated 6mm2 house wire be OK? 

One spike, 6mm insulated (green with yellow tracer) in pvc piping is good. 

[Antonio de Sa]

3 minutes ago, BritishRacingGreen said:

One spike, 6mm insulated (green with yellow tracer) in pvc piping is good. 

One cannot be sure that 1 spike is enough, depends on many things, the only way it to teste it with an earth tester, a good earth should be less than 6 ohms. 

[frivan]

If earthing your panels makes you sleep better, add many earths. But know that if lightning strikes your house, most electronics will be fried.

[Chris_S]

5 minutes ago, frivan said:

If earthing your panels makes you sleep better, add many earths. But know that if lightning strikes your house, most electronics will be fried.

Its more for the coc and insurance company

[Antonio de Sa]

8 minutes ago, frivan said:

If earthing your panels makes you sleep better, add many earths. But know that if lightning strikes your house, most electronics will be fried.

Agree with you 100% had such an incident about 2 years ago, as you said it fried most of my electronics appliances in my house, all that was saved was appliances with external power supplies. And pray that you are not in the shower. 

Edited February 4, 2023 by Antonio de Sa

[frivan]

2 hours ago, Chris_S said:

Its more for the coc and insurance company

For CoCs and insurance you must do what they want. In terms of safety I would prefer one earth. If you have to go to multiple earths, you want to connect them all together with big conductors. Otherwise lightning hitting close to your house may choose to make some loops through your house.

Edited February 4, 2023 by frivan

[Dylboy]

SANS says extraneous conductive parts to be earthed... So earthing is then a must. However panels are class 2 but with earthing points... Whole kettle of fish and actually there is no written rule as such yet.

Lighting protection is very different to earthing and earthing is different to bonding. 

One day there will be a black and white answer.

 

[Chris_S]

3 hours ago, Dylboy said:

SANS says extraneous conductive parts to be earthed... So earthing is then a must. However panels are class 2 but with earthing points... Whole kettle of fish and actually there is no written rule as such yet.

Lighting protection is very different to earthing and earthing is different to bonding. 

One day there will be a black and white answer.

 

So earthing panels to an earth spike should be fine for coc? 

[Dylboy]

3 minutes ago, Chris_S said:

So earthing panels to an earth spike should be fine for coc? 

Not quite as you would require to do an earth resistance test but the result required is not published, anything around 12ohms is good but to get that you may have to drive a 59meter rod... 

From what I have been reading and learning with other sparks and documents is that if you use an earth spike you need to still bond it with the installation earth, so with that just run the earth cable to the earth of the DB. So if you want run a spike but also a cable to the DB. 

 

The honest answer is there is no answer and it is what ever that spark is happy to sign. 

 

Thing is bonding is done to 2ohm, and minimum of 2.5mm cable, lighting protection is 16mm and 6mm depending. 

At the end of the day ask the spark who is going to do the CoC.

 

The honest truth is any installation done DIY should not get a CoC at all as it was not done under the general controll of a wireman... Only if property is sold would a CoC then be conducted.

There are loop holes galore and no public knowledge and the industry as a whole is confused and it's the wild west. 

 

So do what ever the spark wants who will sign it off for you. Insurance also don't care and just want the paper as a tick box. 

[BritishRacingGreen]

4 hours ago, Dylboy said:

Lighting protection is very different to earthing and earthing is different to bonding

My opinion is @Dylboyhas given some very quality remarks here.

So before we get too pedantic, he rightly points points out that bonding and protection are 2 different functions. Bonding to earth neatral is important to have absolute good earth impedance (fault current return path eg.) 

The sole reason for pv earth spike is to have a good low resistance path to earth to relay surges.  So introduce quality wiring procedure, a good earth spike joint, and call it a day. 

[Chris_S]

@Dylboy @BritishRacingGreen

Thank you both for your replies. I'm going to do both probably. I'll run a 6mm earth cable with the PV cables and earth the panels to the PV DB which is earthed to main DB. Then I'll run a 6mm cable to an earth spike. Sparky shouldn't fault that. 

[Shaks]

You need to first understand the Schlemburger method of earthing,as this is the way that you test earth resistance.With this method,a minimum of 2 earth spikes must be used.Secondly,single point earthing is a must on most residential TNC electrical connections.Thirdly,you must bond all the panels and then ground to the earth spike with 16mmsq earthing cable.Drpending on your lightning zone,you might be required to have an air termination rod and/or Type 1 lightning protection.

[coffeedogsjujitsu]

On 2023/02/04 at 10:53 AM, BritishRacingGreen said:

I think it is a requirement. In any case the seperate earth spike and routing is safer for you and your building. Remember the lightning attack surface on pv frames is huge, and you will want the high current surges not to enter your building inner, rather arrest it via a seperate route. 

No naughty person, you will create a potential difference between earth spikes if they are not bonded. Let's blow the roof off ,jump ,jump

 

[wannchev]

Lightning strike density on the highveld is very high. I earthed my '80's TV mast correctly and all i got was cracked window  glass when the lightning struck. So i removed the TV mast and the lightning now strikes my neighbours house on the roof corners ( loose or missing bricks.) So i would link solar steel frames together and run a single lead to earth against a solid wall. Preferably aluminium strap or a piece of ABC conductor cable. You want the earth still to be there the next day. A water pipe is the best bet. Avoid connecting the inverter and its battery to the same earth. Connect these items to the house earth.You dont want any spikes going into the house. 

[BritishRacingGreen]

1 hour ago, coffeedogsjujitsu said:

No naughty person, you will create a potential difference between earth spikes if they are not bonded. Let's blow the roof off ,jump ,jump

 

@coffeedogsjujitsu while this is a public forum where opinions and informal comments are most welcome, I do feel you should have done a slight more homework and research before making a bold statement this.

Let me help you here, you are not dealing with the reticulated neatral connection in your residential bounds. The frame substructure of pv has no reference to your live and earth-bonded neatral. We are trying to earth these frames against lighning surges and plus minus nothin else. 

And no, the roof will only blow off  in the Netflix movies. 

[Moderator2]

[1ougat]

The misunderstandings of safety earthing ,bonding and earthing for lightning is scary. Lightning earthing is also part science and black art

1.The lightning incused spikes are a high frequency Voltage spike  that travel on the conductors ( Neutral , Live , Earth - it does not care ) towards your precious inverter - and it will also do so on your DC wires . At  a reflection point on the line it will reflect and effectively double up and can spark over at such a point . It is why you see arcing horns sometimes on overhead lines and the good munics will install surge arrestors on the incoming lines at the supply transformer. In the high voltage case you also will then have the 50hz power going to ground at such a breakdown point and effectively creating a short circuit that the upstream breakers must clear . That can cause damage as the time could be long before the breaker operates .(Long is also relative as this would be a few cycles for the breaker to operate vs the lightning induced spike timeline.    Suffice to say you want all your equipment to rise together on this voltage so that the differencial between the equipment don't exceed the equipment rating .  So add as many earths as you can, connect them together and add surge arrestors on your incoming feeds . And buy insurance. Some connections I have seen would not have helped in a lightning strike but at least would satisfy the insurance guy that you had an earth as required . 

2.Bonding is there that you are not the earth conductor that closes the loop in case there is a live wire touching exposed metal .

3. Safety earthing is there to ensure that your earth leakage works properly in case of any current (more than 25mA)returning on the earth wire. 

Earthing is a very interesting subject and can be confusing to people . 

Hope this helps 

 

 

 

[AlexCape]

Please correct me if I am wrong..

There are 2 issue here? One is to protect you from the PV voltage generated, should there be an electrical fault and you touch something live. Two is protection from lightening.

Re (One), I think there are no requirements if the DC voltage is below 110v. I have used multiple strings with the lowest voltage possible to allow the 48v inverter to work efficiently, when the battery charging voltage needs to be the highest. A 72 cell panel in series with a 60 cell panel gives an OC v of less than 90v, and at max power still around 70v, more than 10v above max battery charge voltage (lead acid) which is sufficient. Playing around it seems 6v is required between PV voltage and battery voltage for efficiency.

If (One) is addressed, and there is no connection whatsoever to the grid, then (Two) is pretty much voluntary?

Edited February 6, 2023 by AlexCape
Typo

[Yellow Measure]

22 minutes ago, AlexCape said:

Please correct me if I am wrong..

There are 2 issue here? One is to protect you from the PV voltage generated, should there be an electrical fault and you touch something live. Two is protection from lightening.

Re (One), I think there are no requirements if the DC voltage is below 110v. I have used multiple strings with the lowest voltage possible to allow the 48v inverter to work efficiently, when the battery charging voltage needs to be the highest. A 72 cell panel in series with a 60 cell panel gives an OC v of less than 90v, and at max power still around 70v, more than 10v above max battery charge voltage (lead acid) which is sufficient. Playing around it seems 6v is required between PV voltage and battery voltage for efficiency.

If (One) is addressed, and there is no connection whatsoever to the grid, then (Two) is pretty much voluntary?

Regarding (One), the serial strings of modern inverters can carry up to 500V, some even over that. It's far more efficient than low voltage, because thinner cable can be used. A DC arc is not an AC arc, very different, it is sustained and as a result a whole lot hotter, which is a source of fire. This over and above electrocution. And regarding low voltage / high amperage strings, if we believe Mike Holt, 35mA is all that it takes for the heart to reach fibrillation.

Regarding (2), I don't think that protection from an actual direct strike is called for, there's not much that one can do cheaply if that is the case. When people talk about lightning strike and roof / panels, they are mostly referring to the induced voltage that a nearby strike could cause.    

   

[TaliaB]

 The way i do it is to use an earth strap from the PV panels to the shortest path to a earth via an earth spike. Join an earth wire from the earth point on the PV panel and take it directly to the DB main earth connector(PE) This way there can be no potential difference between the two points, as all water pipes in the house are connected to this earth, usually at the geyser position. If lightning strikes the roof or panels, it will be directed to earth via the shortest path.
By joining the two earths, with a minimum of a 6mm square multi strand wire, or preferably a flat strap, then you nullify this earth potential difference across the two points. With lightning strikes no way of doing it may be certain.

[Chris_S]

2 hours ago, YellowTapemeasure said:

Regarding (One), the serial strings of modern inverters can carry up to 500V, some even over that. It's far more efficient than low voltage, because thinner cable can be used. A DC arc is not an AC arc, very different, it is sustained and as a result a whole lot hotter, which is a source of fire. This over and above electrocution. And regarding low voltage / high amperage strings, if we believe Mike Holt, 35mA is all that it takes for the heart to reach fibrillation.

Regarding (2), I don't think that protection from an actual direct strike is called for, there's not much that one can do cheaply if that is the case. When people talk about lightning strike and roof / panels, they are mostly referring to the induced voltage that a nearby strike could cause.    

   

Watching that video I can take this away. 

1. Earthing your panels to your DB is no good as the panels are not in the AC system. Breakers won't trip. That's why we use DC over current breakers or PV fuses. 

2. Grounding panels to a ground rod is only needed to attempt to protect equipment from transient over voltage conditions. 

[Chris_S]

It seems like it's different rules around the world. Australia say panels must be earthed to the inverter earth ie main DB earth with a low resistance. 

USA you must have 2 earth spikes.